Postbank most useless bank around

I get an sms from + ********** ********** 74 Postbank alert wishing me a happy birthday and thanks for banking with us. The problem is the sms has no name or account number. The other problem is it is not my birthday and I have never ever had a Postbank account. I wrote to them to stop. The reply give us your cellphone number so we can check. No that is not going to happen. Giving out my cellphone number is phising. They just shooting blind. Sending random messages to anyone. Why don't they verify the customers cellphone numbers at the time the account is opened.